U.S. Pat. No. 3,861,619, assigned to the assignee of the present invention, recognized the desirability of automatic detection of the ends of the length of magnetic tape within reel-to-reel tape cartridges. That patent provided a length of magnetic tape which was formed adjacent each end with a repetitive pattern of holes, the patterns of holes at the two ends of the tape being different to distinguish the ends of the tape from each other. Two additional sets of holes, located more centrally of the length of tape, were also provided to demark the ends the desired recording area of the length of recording tape.
This system worked well and was adequate when there existed only a limited variety of cartridge types and the length of tape and useful recording area was the only information necessary to successfully utilize the cartridges. Since that time, however, there has been a proliferation of cartridge types wherein the cartridges vary not only in tape length but also in such things as tape width and coercivity of the tape itself.
In order to utilize the present variety of cartridge types, the tape recorder must be able to sense numerous factors in addition to merely tape length.